Researchers have found evidence that a direct interaction between vitamin D and a common genetic variant alters the risk of developing multiple sclerosis (MS). The Oxford University-led research, published in PLoS Genetics, suggests that vitamin D deficiency during pregnancy and the early years may increase the risk of offspring developing MS later in life.
MS is the most common disabling neurological condition affecting young adults. More than 85,000 people in the UK and 2.5 million worldwide are thought to suffer from the condition, which results from the loss of nerve fibres and their protective myelin sheath in the brain and spinal cord, causing neurological damage.
The causes of MS are unclear, but both environmental and genetic factors play a role. Previous studies have shown that populations from Northern Europe have increased risk of MS risk if they live in areas receiving less sunshine. This supports a direct link between deficiency in vitamin D, which is produced in the body through the action of sunlight, and increased risk of developing the disease.
The largest genetic effect by far comes from the region on chromosome six containing the gene variant known as DRB1*150 and from adjacent DNA sequences. While one in 1,000 people in the UK are likely to develop MS, this number rises to around one in 300 among those carrying a single copy of the variant and one in 100 of those carrying two copies.
Now researchers at the University of Oxford and the University of British Columbia have established a direct relationship between DRB1*1501 and vitamin D.
The study funded by the UK's MS Society, the MS Society of Canada, the Wellcome Trust and the Medical Research Council, found that proteins activated by vitamin D in the body bind to a particular DNA sequence lying next to the DRB1*1501 variant, switching the gene on.
‘In people with the DRB1 variant associated with MS, it seems that vitamin D may play a critical role,’ says Dr Julian Knight from the Wellcome Trust Centre for Human Genetics at the University of Oxford. ‘If too little of the vitamin is available, the gene may not function properly.’
'We have known for a long time that genes and environment determine MS risk,' says Professor George Ebers of the Department of Clinical Neurology. ‘Here we show that the main environmental risk candidate – vitamin D – and the main gene region are directly linked and interact.’
Professor Ebers and colleagues believe that vitamin D deficiency in mothers or even in a previous generation may lead to altered expression of DRB1*1501 in offspring.
‘Our study implies that taking vitamin D supplements during pregnancy and the early years may reduce the risk of a child developing MS in later life,’ says lead author Dr Sreeram Ramagopalan. ‘Vitamin D is a safe and relatively cheap supplement with substantial potential health benefits. There is accumulating evidence that it can reduce the risk of developing cancer and offer protection from other autoimmune diseases.’